Insect lipoprotein metabolism is an excellent model system for the study of lipid transport processes: the insect lipoprotein system is simple since only one multifunctional lipoprotein, the lipophorin, is present in insect hemolymph. Further, insect lipophorin functions as a reusable lipid shuttle, transporting lipids throughout the insect body without being degraded. In this aspect it proves to be a good model system for the delivery of cholesterol ester by mammalian HDL and LDL in the absence of internalization of lipoproteins into the cell. Recently, a lipid transfer particle (LTP) was isolated from insect hemolymph. This insect LTP is the first lipid transfer particle shown to enhance net lipid transfer from cell to lipoprotein. These results make the study of insect lipoprotein metabolism as a model system even more attractive. The long-term aim of this research proposal is to increase knowledge on fundamental aspects of lipoprotein metabolism, especially the transfer of lipid between cell and lipoprotein, using the insect model system as a replacement of vertebrate model systems. Better understanding of insect lipid metabolism is important in the control of migratory insects. More specifically the mechanism of LTP-mediated diacylglycerol transfer from fat body cell to the insect lipoprotein will be studied using monoclonal antibodies to LTP. Involvement of LTP-apoproteins in the lipid transfer activity, as well as the interaction of LTP with the plasma membrane of the fat body cell, will be investigated. One of the main and best studied functions of lipophorin is the transport of diacylglycerol to the active flight muscle. The role of LTP in this process will be investigated, and the flight muscle lipophorin lipase, the rate-limiting enzyme in the fatty acid delivery to the flight muscle cell, will be studied in more detail. The lipase will be purified and antibodies will be raised against it.